diff --git a/.github/workflows/ccpp.yml b/.github/workflows/ccpp.yml
index eb52a9e4..ba0d61c2 100644
--- a/.github/workflows/ccpp.yml
+++ b/.github/workflows/ccpp.yml
@@ -66,7 +66,7 @@ jobs:
         path: 'fluxengine-testdata'
     - name: brew
       run: |
-        brew install sqlite pkg-config libusb protobuf wxwidgets fmt make coreutils dylibbundler libjpeg libmagic nlohmann-json cli11 boost glfw3 md4c ninja python freetype2 mbedtls@3
+        brew install sqlite pkg-config libusb protobuf wxwidgets fmt make coreutils dylibbundler libjpeg libmagic nlohmann-json cli11 boost glfw3 md4c ninja python freetype2 mbedtls@3 lunasvg
         brew link mbedtls@3
         brew upgrade
     - name: make
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index e2b98969..f72dd80f 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -101,7 +101,7 @@ jobs:
 
     - name: brew
       run: |
-        brew install sqlite pkg-config libusb protobuf wxwidgets fmt make coreutils dylibbundler libjpeg libmagic nlohmann-json cli11 boost glfw3 md4c ninja python freetype2 mbedtls@3
+        brew install sqlite pkg-config libusb protobuf wxwidgets fmt make coreutils dylibbundler libjpeg libmagic nlohmann-json cli11 boost glfw3 md4c ninja python freetype2 mbedtls@3 lunasvg
         brew link mbedtls@3
         brew upgrade
 
diff --git a/Makefile b/Makefile
index 09942532..8a3b756f 100644
--- a/Makefile
+++ b/Makefile
@@ -43,11 +43,11 @@ ifeq ($(BUILDTYPE),windows)
 else
 	CC = clang
 	CXX = clang++
-	CFLAGS = \
+	CFLAGS += \
 		$(OPTFLAGS) \
 		-I/opt/homebrew/include -I/usr/local/include \
 		-Wno-unknown-warning-option
-	CXXFLAGS = \
+	CXXFLAGS += \
 		$(OPTFLAGS) \
 		-std=c++23 \
 		-fexperimental-library \
@@ -56,7 +56,7 @@ else
 		-Wformat-security \
 		-Wno-deprecated-enum-float-conversion \
 		-Wno-deprecated-enum-enum-conversion
-	LDFLAGS =
+	LDFLAGS +=
 	AR = ar
 	PKG_CONFIG = pkg-config
 	ifeq ($(BUILDTYPE),osx)
@@ -67,7 +67,7 @@ endif
 
 HOSTCC = gcc
 HOSTCXX = g++ -std=c++20
-HOSTCFLAGS = -g -O3
+HOSTCFLAGS += -g -O3
 HOSTLDFLAGS =
 
 REALOBJ = .obj
diff --git a/build/pkg.py b/build/pkg.py
index e1adec53..b3c2d589 100644
--- a/build/pkg.py
+++ b/build/pkg.py
@@ -37,6 +37,7 @@ def get_property(self, name, flag):
 
 def _package(self, name, package, fallback, pkgconfig):
     if pkgconfig.has_package(package):
+        print(f"package '{package}' found")
         cflags = pkgconfig.get_property(package, "--cflags")
         ldflags = pkgconfig.get_property(package, "--libs")
 
@@ -50,6 +51,7 @@ def _package(self, name, package, fallback, pkgconfig):
         return
 
     assert fallback, f"Required package '{package}' not installed"
+    print(f"package '{package}' not found; using fallback")
 
     if "cheader_deps" in fallback.args:
         self.args["cheader_deps"] = fallback.args["cheader_deps"]
diff --git a/doc/building-client.md b/doc/building-client.md
index 10de90eb..7298dcd0 100644
--- a/doc/building-client.md
+++ b/doc/building-client.md
@@ -11,15 +11,17 @@ install some support packages. **You will need to check out git with submodules
 
   - For Linux with Ubuntu/Debian:
     `libudev-dev` `libsqlite3-dev` `protobuf-compiler` `libfmt-dev`
-    `libprotobuf-dev` `libmagic-dev` `libmbedtls-dev`
-    `libcurl4-openssl-dev` `libmagic-dev` `nlohmann-json3-dev`
-    `libdbus-1-dev` `libglfw3-dev` `libmd4c-dev` `libfreetype-dev`
-    `libcli11-dev` `libboost-regex-dev`
+    `libprotobuf-dev` `libmagic-dev` `libmbedtls-dev` `libcurl4-openssl-dev`
+    `libmagic-dev` `libdbus-1-dev` `libglfw3-dev` `libfreetype-dev`
+    `libboost-regex-dev` Plus, optionally (if not present, internal versions
+    will be used): `nlohmann-json3-dev` `libcli11-dev` `libmd4c-dev`
   - For OSX with Homebrew:
     `sqlite` `pkg-config` `libusb` `protobuf` `fmt` `make` `coreutils`
-    `dylibbundler` `libjpeg` `libmagic` `nlohmann-json` `cli11` `boost`
-    `glfw3` `md4c` `ninja` `python` `freetype2` `mbedtls`
+    `dylibbundler` `libjpeg` `libmagic`  `boost` `glfw3` `ninja` `python`
+    `freetype2` `mbedtls` Plus, optionally (if not present, internal versions
+    will be used): `nlohmann-json` `cli11` `md4c` `lunasvg`
   - For Windows with MSYS and pacboy:
+    `python` `diffutils` `ninja` `make` `zip` `mingw-w64-cross-clang`
     `protobuf:p` `pkgconf:p` `curl-winssl:p` `file:p` `glfw:p` `mbedtls:p`
     `sqlite:p` `freetype:p` `boost:p` `gcc:p` `binutils:p` `nsis:p`
     `abseil-cpp:p`
diff --git a/src/gui2/build.py b/src/gui2/build.py
index 2c7bd954..33446f94 100644
--- a/src/gui2/build.py
+++ b/src/gui2/build.py
@@ -44,19 +44,35 @@ def sources_from(path, except_for=[]):
 package(name="magic_lib", package="libmagic")
 package(name="mbedtls_lib", package="mbedtls")
 
-cxxlibrary(
+package(
     name="nlohmannjson_lib",
-    srcs=[],
-    hdrs=headers_from("dep/nlohmann_json/single_include"),
+    package="nlohmann_json",
+    fallback=cxxlibrary(
+        name="nlohmannjson_fallback_lib",
+        srcs=[],
+        hdrs=headers_from("dep/nlohmann_json/single_include"),
+    ),
 )
 
-clibrary(
+package(
     name="md4c_lib",
-    srcs=sources_from("dep/md4c/src"),
-    hdrs={"md4c.h": "dep/md4c/src/md4c.h"},
+    package="md4c",
+    fallback=clibrary(
+        name="md4c_fallback_lib",
+        srcs=sources_from("dep/md4c/src"),
+        hdrs={"md4c.h": "dep/md4c/src/md4c.h"},
+    ),
 )
 
-cxxlibrary(name="cli11_lib", srcs=[], hdrs=headers_from("dep/cli11/include"))
+package(
+    name="cli11_lib",
+    package="CLI11",
+    fallback=cxxlibrary(
+        name="cli11_fallback_lib",
+        srcs=[],
+        hdrs=headers_from("dep/cli11/include"),
+    ),
+)
 
 if config.osx:
     clibrary(
@@ -95,12 +111,16 @@ def sources_from(path, except_for=[]):
     cflags=cflags,
 )
 
-cxxlibrary(
+package(
     name="lunasvg",
-    srcs=sources_from("dep/lunasvg/source"),
-    hdrs=headers_from("dep/lunasvg/include"),
-    deps=[".+plutovg", "+fmt_lib"],
-    cflags=cflags,
+    package="lunasvg",
+    fallback=cxxlibrary(
+        name="lunasvg_fallback_lib",
+        srcs=sources_from("dep/lunasvg/source"),
+        hdrs=headers_from("dep/lunasvg/include"),
+        deps=[".+plutovg", "+fmt_lib"],
+        cflags=cflags,
+    ),
 )
 
 cxxlibrary(